Anne Lemnitzer

University of California, Irvine

Research

My primary research interest is at the interface of geotechnical and structural earthquake engineering, studying the response mechanisms of sub-and superstructure elements and systems. My current and past research projects include the experimental studies and numerical evaluation of deep foundation systems, underground structures and embankment systems, as well as the response of structural components to static and dynamic loading via large scale testing (field/lab), model scale testing (centrifuge/shake table) and analytical-numerical frameworks. I am also interested in the development of innovative instrumentation schemes and sensor technology applicable to soil structure interaction (SSI) studies. My research in deep foundations also includes the exploration of high performance materials that reduce the carbon footprint in conventional foundation design.

I am furthermore interested in studying the influence of SSI on structural components and systems through case and field studies, model/large-scale testing and numerical and parametric simulations. Studies pertaining to the structural response behavior due to ground excitation include the assessment of building components (e.g., moment resisting frame components and cladding systems), as well as the investigation of retrofit and strengthening mechanisms for structurally damaged components.

Interests

Foundation Engineering

Soil-structure interaction

Infrastructure response under hazard loading

Development of sensor instrumentation

Large-scale testing

Earthquake engineering

Selected Research Projects

Lateral stresses during the installation of drilled displacement piles

In recent years, the use of DD piles in the U.S. has increased, and these elements have been used as structural foundations (e.g., support for column loading) and for ground improvement (e.g., column-supported embankments) on commercial and public work projects. Historically, DD piles have been installed with diameters ranging from about 12- to 26-inches (300 to 675 mm) and to a maximum depth of approximately 125 ft (38m), whereby the geometry of the pile (diameter and depth) are directly related to the capability of the drill rig used to construct a DD pile.

During the advancement and extraction of the tooling, displacement (via radial compaction) of the in-situ soil is required for this technique to be effective. Understandably, a considerable amount of mechanical work (e.g., energy and power) is required by the drill rig to displace the volume of soil necessary to create the desired size of the DD pile. At the location of the tooling in the ground, the tool itself imparts compactive stresses and shearing stresses to the soil during the construction of the DD pile. Various contractors and researchers have reported on the different design approaches / assumptions used, equipment and tooling, benefits of DD piles, and QC/QA protocol. However, no concerted effort has been reported or is available in the published literature discussing the effects and geometrical extents (e.g., on aesthetics and long-term performance) of radially and vertically induced stresses on adjacent structures (e.g., earth retaining structures, basement / tunnel walls, and utility duct banks) resulting from the construction of DD piles.

Using pressure sensor instrumentation, CPT testing, and dilatometer results this research will measure and quantify the radial effect and extent of the lateral stresses (and displacements, where possible) due to the advancement and extraction of the tooling. The information garnered through this study provides an immediate scientific knowledge on the near-field and far-field lateral stresses developed during and after pile installation and a long-term basis for contractors and designers to reduce their risk exposure when DD piles are intended to be installed in close proximity to existing structures.

Field testing as well as model-scale testing in the UCI soil pit will constitute the experimental part of this research, accompanied by numerical modeling studies and laboratory data.

Funding Agency: Deep Foundations Institute (DFI)

Time Frame: 10/2016 – present

Towards Next Generation P-Y Curves - Part 1: Evaluation of the state of the art and identification of recent research developments

This research program consists of a well-coordinated literature study of analytical, model-scale and large-scale deep foundation systems under lateral loading with the objective to (i) identify limitations with existing p-y curves & p-y design recommendations, (ii) summarize recent research that can help address these limitations, and (iii) identify additional research needs required to formulate Next Generation P-Y (NGPY) relations. The specific outcome consists of a comprehensive report which will compile foundation studies performed in the last 40 years and help develop a new set of “Next Generation P-Y Curves” in the near future.

Funded by: Pacific Earthquake Engineering Research Institute (PEER)

Project Info

Levees and Earthquakes: Averting an Impending Disaster

This study evaluated the performance of liquefiable and non-liquefiable embankment systems in California’s Delta region. Study objectives included the overall performance behavior under various levels of ground shaking and the investigation of settlement mechanisms pertaining to the soft underlying soils (peat).

Seismic soil pressures: U.S. Instrumentation and data processing of a large-scale experiment on soil-structure interaction of underground structures on the E-Defense shake table in Miki, Japan

Sensor instrumentation to capture seismic soil pressures on large scale vertical underground components were developed and installed to gain insight in the nonlinear dynamic response of subsurface elements different from conventional walls or piles. Experimental studies are complements with numerical modeling and the development of simplified design charts for non-rigid subsurface elements.

Rock socketing of drilled shafts is an attractive anchor- and load-transfer mechanism for axially loaded piles subject to compression or uplift forces. Simultaneously, rock-socketed piles provide stable embedment fixity when lateral loads or rotational moments need to be transferred along the pile length into sufficient depth where fixity can be guaranteed.

Good understanding has been gained and published for axially loaded shafts; however, uncertainties exist for laterally loaded piles in rock sockets when designed using Winkler based analysis models. Currently no experimental data exist to verify the pile behavior and the development of internal moment and shear forces of rock-socketed piles under lateral loading. Simultaneously only very few numerical studies exist which investigate this particular problem. To address our current, limited knowledge in correctly estimating and designing for the actual shear demand in piles along the rock-soil boundary, the proposed research will consist of a well- coordinated combination of analytical studies, and development of an experimental program and the execution of baseline load tests on 2-6 pile shafts.

Large -scale testing of RC SMRF beams with openings under cyclic loading: Experimental and numerical studies

This research project investigates the nonlinear response behavior and cyclic performance of moment resisting frame beams with and with out openings. Experimental and numerical studies provide insight into the opportunity and challenge of openings in structural elements that are part of lateral force resisting systems. Failure patterns, hinge development, and interaction mechanisms are studied and complemented by parametric simulations. The behavior of and performance of the specimens strengthened with FRP schemes is also investigated via large scale testing.

Findapile.com is the first and most comprehensive online platform that collects and synthesized lateral load test data for large scale pile tests. Over 70 pile load tests are implemented in the searchable database, with general data such as load-deflection, soil properties and p-y formulations. A full reference to the original research work is provided. The database is established, authored and maintained by Prof. Lemnitzer.

Analytical studies on the inertial and kinematic response behavior of laterally loaded pile foundations include a proposed continuum solution for lateral soil resistance due to pile motion, the development of new and simple formulation for a dynamic Winkler modulus, closed form expressions for pile stiffness and damping, a study of the effect of pile tip fixities and impedance contrasts, as well as the development of a frequency dependent Winkler modulus for kinematic load applications.